Any property with 5 units or more is valued based on cap rate and the NOI, net operating income. I don't invest in larger multi-families like this yet, but I am in the research phase, learning all I can about investing in larger multi-families. Right now I have one duplex. I am researching syndicating apartment building, so raising money from investors to buy an apartment building. I have found biggerpockets.com and themichaelblank.com very useful for information about real estate investing in general, and raising money to purchase apartment buildings, respectively.